Deposition of for instance wax on the inner wall of oil pipelines is a severe problem in today's oil production infrastructure. When warm oil flows through a pipeline with cold walls, wax will precipitate and adhere to the walls. This in turn will reduce the pipeline's cross-sectional area, which without counter measures will lead to a loss of pressure and ultimately to a complete blockage of the pipeline.
To this end, it is of interest to measure or otherwise determine the thickness of any deposit of material on the inner wall of a pipeline.
Known techniques for measuring or otherwise determining the thickness of any deposit of material on the inner wall of a pipeline include pressure pulsing and measuring the deposit removed in a pig (pipeline inspection gauge) removal operation.
However, a drawback with pressure pulsing is that the accuracy is low. Further, measuring the deposit removed in a pig removal operation gives no information about the deposit distribution along the pipeline.